1. Field of the Invention
The present invention relates to an adapter that is interposed between a steering wheel and a boss and that enables attachment and detachment of the steering wheel to and from the boss.
2. Description of the Related Art
Conventionally, one way to prevent vehicle theft is to remove the steering wheel from the boss. In a vehicle such as an automobile, a steering wheel (handle) controlled by a driver is securely attached to a boss that supports a shaft. Because turning the steering wheel controls the vehicle, removing the steering wheel makes it impossible to drive the vehicle.
Thus, in order to facilitate attachment and detachment of the steering wheel, as disclosed in Japanese Unexamined Patent Application Publication No. JP-A 2003-72559, etc., a technique of interposing a steering wheel adapter between a steering wheel and a boss has become prevalent.
A conventional steering wheel adapter comprises a plate attached to a steering wheel, a base attached to a boss, and a ring that covers the periphery of the base. On the contacting faces of the plate and the base, a concave and a convex that can be engaged with each other are disposed, respectively. Moreover, on the plate and the ring, a plurality of protrusions extending in a direction orthogonal to the shaft axis are formed, respectively. When the ring is rotated in a state where the plate is mounted on the base, and the ring-protrusion is located above the plate-protrusion, the plate-protrusion and the ring-protrusion come in contact with each other in the shaft axis direction.
The steering wheel adapter, whose concave and convex are engaged when the plate is mounted on the base, prevents the steering wheel from rotating with respect to the boss. Moreover, by rotating the ring to locate the ring-protrusion above the plate-protrusion, the plate-protrusion and the ring-protrusion come in contact with each other in the shaft axis direction, and the steering wheel is prevented from slipping off from the boss in the shaft axis direction.
Therefore, this steering wheel adapter makes it possible to easily connect the steering wheel to the boss by mounting the plate attached to the steering wheel on the base attached to the boss and rotating the ring. Conversely, when the ring is rotated reversely, the steering wheel can slip off from the boss.
The conventional steering wheel adapter prevents a slip-off in the shaft axis direction by using the protrusions formed on the plate and the ring, as described above. However, in a case where a gap between the plate-protrusion and the ring-protrusion in the shaft axis direction is small, the protrusions hit each other when it is intended to rotate the ring, and a substantial force is required to rotate the ring. Therefore, it has been hard to say that attachment and detachment of the steering wheel is easy for women.
Conversely, in a case where the gap between the plate-protrusion and the ring-protrusion in the shaft axis direction is large, it is easy to rotate the ring to attach and detach the steering wheel. However, it causes the plate to lift up by a length of the gap, and rattle occurs in the shaft axis direction at the time of control of the steering wheel.